Such a one-part contact element is known from the EP 0 133 094 B1. This describes a connecting terminal whose one end region is to be connected to a connecting cable, while the other connecting region serves to receive a plug pin, e.g. from a spark plug or a spark plug connector. For joining to the end of the connecting cable, a ferrule situated in the end region of the connecting terminal is clipped onto the insulating sheath and the insulation-free end of the cable and crimped onto it. This ferrule is followed by a helically wound bush which can be clipped onto a contact pin of the operational element (spark plug, spark plug connector). For this purpose the contact pin of the operational element has a groove into which can snap a hook projecting from outside through apertures in the windings of the contact bush. During the clip-on process the contact bush springs up so that, after the snapping in, it can again return to its original circumference.
Such an arrangement is advantageous as it ensures a secure contact between the connecting cable and the electric operational element and the one-part connecting terminal allows for economical manufacture.
The drawback however is that because of the releasability of the catch, it cannot be used as a contact element between an ignition cable and a spark plug connector. Non-releasable contact elements are used in prefabricated spark plug connectors for connecting the ignition cable, i.e. spark plug connectors which are encased in a spray coated insulation layer. The link between the contact bush and the spark plug connector must therefore be so resistant that when the plug arrangement constructed in this way is subjected to tensile forces, only the spark plug connector becomes separated from the spark plug, as required for servicing.
In the DE 8313411 U1 is disclosed an arrangement in which a bush can be clipped to a contact pin of a spark plug connector and is non-releasably snap-corrected thereto. For this the contact pin of the operational element has a snap-in groove into which can snap a spring washer of the connecting bush of the connecting cable. The spring washer is trapezoidal in design and a substantial part of its circumference lies outside in a groove of the connecting bush. The straight segment of the spring washer penetrates a radial opening of the bush and projects with one part of its circumference beyond the inner sheath of the bush. The segment serves for snap connection in a corresponding groove of the contact pin. During the manufacture of the contact bush, the spring washer is received in the arrangement as a separate part. This multiplicity of parts in the contact bush increases the manufacturing cost and is therefore undesirable.